Caulobacter, a stalked bacterium with well defined morphologic stages in its life cycle, is proposed as a procaryotic model for the study of cell differentiation. Understanding the basic mechanisms of control of cellular differentiation has important implications in several areas of biomedical research including normal and aberrant embryological development, tumor control and development, and studies of natural aging. Characterization of the basic genetics of Caulobacter will be performed for the purpose of better defining the control mechanisms of the maturation process from motile, non-stalked cell to non-motile stalked form. The basic genetics of this organism will be studied using our recently developed mating system. Homogeneous populations of each of the two stages will be tested for the capacity to mate. A determination that sexuality resides in one or the other stage will provide an important additional characteristic of differentiation heretofore unknown in this genus and provide a convenient marker in addition to the already recognizable morphologic markers for the study of the stepwise processes in maturation. We will use several techniques for the separation of the cell types including selective bacteriophage infection with phage 06 which we have shown in flagella-trophic and can infect only the motile stage. We will identify similarities and differences between the Caulobacter genetic system and the other better known microbial systems. We will develop additional auxotrophic, maturation variant, temperature sensitive and other appropriate mutants for the mapping of the bacterial genome.